Display processor

ABSTRACT

A display processor for suppressing the occurrence of crosstalk. The display processor according to the present invention includes: an average obtaining unit which obtains the average of pixel values in a predetermined area on a line; a difference value operation unit which calculates a pixel difference value between the average pixel value and the pixel value of a target pixel to be corrected; and a processing unit which corrects the target pixel value according to the pixel difference value. Since the occurrence of crosstalk is suppressed by means of signal processing, it is unnecessary to use any complicated expensive structure. This makes it possible to achieve a display processor easy to control. The processing unit may also obtain a variation in pixel value near the target pixel to be corrected, and correct the target pixel value according to this variation.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a display processing technologyfor displaying an image, and more particularly to a display processingtechnology for suppressing the occurrence of crosstalk.

[0003] 2. Description of the Related Art

[0004] Presently, the displays of portable communication terminals andpersonal computers are composed principally of liquid crystal panels.For displays of the next generation as alternatives to the liquidcrystal panels, organic electroluminescence panels and inorganicelectroluminescence panels have been a focus of recent attention. Suchdisplays are provided with pixels arranged in a matrix, and are drivenchiefly by two types of driving systems, or an active matrix drivingsystem and a passive matrix driving system.

[0005] Among important issues concerning the displays is the occurrenceof horizontal or vertical crosstalk. A crosstalk phenomenon refers toone in which a fixed pattern such as a window is displayed withbrightness variations in areas horizontally adjoining the pattern. Thebrightness variations are considered to result from voltage drops onelectrode lines, the voltage drops occurring from high currents flowingthrough the lines.

[0006]FIG. 1 shows an example of a display image in which a crosstalkphenomenon occurs. Suppose the case of displaying a white window on auniform halftone background. On a line A-A′ SA-70123 which includespixels of the window, the input signal level makes such changes in thehorizontal direction as 0.3 in the range from pixel 1 to pixel (p−1),1.0 in the range from pixel p to pixel (q−1), and 0.3 in the range frompixel q to pixel r. On a line B-B′ which includes no window pixel, theinput signal level is maintained at 0.3 across all the pixels. Here, asshown in the diagram, brightness variations are observed in the areas onthe right and left of the window on the horizontal line as compared tothe windowless line. Such brightness variations are unfavorable in termsof quality. Then, there have heretofore been proposed active matrix typeliquid crystal displays comprising crosstalk suppressing informationdetecting means which indirectly detect potential variations of a commonelectrode resulting from changes in a driving voltage of signal wiring,and a filter circuit which corrects the detected potential variations(for example, see Japanese Patent Laid-Open Publication No.2002-123227).

SUMMARY OF THE INVENTION

[0007] Nevertheless, crosstalk suppression is desirably achieved by assimple a configuration as possible.

[0008] It is thus an object of the present invention to provide adisplay processor which performs signal processing capable ofsuppressing the occurrence of crosstalk with a simple configuration.

[0009] To solve the foregoing problem, one of the aspects of the presentinvention provides a display processor. The display processor comprises:a first obtaining unit which obtains an average pixel value, or anaverage of pixel values in a predetermined area on a line; an operationunit which calculates a pixel difference value, or a difference betweenthe average pixel value and a pixel value of a target pixel to becorrected; a processing unit which corrects the target pixel value, orthe pixel value of the target pixel, according to the pixel differencevalue; and a display unit which displays the pixel value corrected.Since the display processor of this aspect corrects pixel values byusing average pixel values, it becomes possible to suppresscrosstalk-based brightness variations effectively by means of signalprocessing.

[0010] The processing unit may comprise a second obtaining unit whichobtains a variation in pixel value near the target pixel, and acorrection unit which corrects the target pixel value according to thevariation. The processing unit preferably decreases the amount ofcorrection of the target pixel value with an increasing variation, andincreases the amount of correction of the target pixel value with adecreasing variation.

[0011] The second obtaining unit may obtain the variation based onadjoining-pixel difference absolute values, or absolute values ofdifferences between the pixel values of pixels adjoining within acertain area near the target pixel. The second obtaining unit may obtainthe variation based on an integrated value of the adjoining-pixeldifference absolute values. If an adjoining-pixel difference absolutevalue exceeds a threshold, the second obtaining unit may determine anintegrated value by subjecting the threshold to the integration insteadof the adjoining-pixel difference absolute value. The second obtainingunit may compare each of the adjoining-pixel difference absolute valuesbetween adjoining pixels within a certain area near the target pixelwith a threshold, and obtain the variation based on the counted numberof adjoining-pixel difference absolute values exceeding the threshold.

[0012] The processing unit may correct the target pixel value accordingto the position of the target pixel on the display unit. The firstobtaining unit may obtain the averages or integrated values of the pixelvalues in predetermined areas on a plurality of lines including theabovementioned predetermined area on the line. Here, the operation unitcalculates a line difference value, or a difference between the averagepixel values or integrated values of the lines, and the processing unitcorrects the target pixel value according to the line difference value.When the display unit is split into a plurality of areas for driving,the processing unit may correct the pixel value of a pixel at a positionsymmetrical to the target pixel in the split area.

[0013] Incidentally, any combinations of the foregoing components, andthe expressions of the present invention converted among methods,apparatuses, systems, and the like are also intended to constituteapplicable aspects of the present invention.

[0014] This summary of the invention does not necessarily describe allnecessary features so that the invention may also be a sub-combinationof these described features.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is a diagram showing an example of a display image in whicha crosstalk phenomenon occurs;

[0016]FIG. 2 is a diagram showing the module configuration of amatrix-driven type display unit;

[0017]FIG. 3 is a diagram showing the configuration of a displayprocessor;

[0018]FIG. 4 is a diagram showing the configuration of a processingunit;

[0019]FIG. 5 is a chart showing an example of a correction level controlcharacteristic;

[0020]FIG. 6 is a diagram showing an image to appear on the display unitand examples of the pixel values, or signal levels, on horizontal lines;

[0021]FIG. 7 is a chart showing an example of a correction gain controlcharacteristic for adjusting the correction level;

[0022]FIG. 8 is a chart for explaining an example of the method forcalculating a variation;

[0023]FIG. 9(a) is a diagram showing an example of display on thedisplay unit and input signal levels when uneven crosstalk occurs, andFIG. 9(b) is a diagram showing signal levels for correcting target pixelvalues according to the positions of the target pixels to be correctedon the display unit;

[0024]FIG. 10(a) is a diagram showing an example of display on thedisplay unit and input signal levels when crosstalk occurs at theboundaries between a crosstalk-occurring area and crosstalk-free areas,and FIG. 10(b) is a diagram showing signal levels for correcting thetarget pixel values by suppressing the crosstalk at the boundaries;

[0025]FIG. 11 is a chart showing another example of the correction gaincontrol characteristic for adjusting the correction level; and

[0026]FIG. 12(a) is a diagram showing an example of display whencrosstalk occurs between symmetrical areas on the display unit, and FIG.12(b) is a diagram showing signal levels for correcting target pixelvalues by suppressing the crosstalk between the symmetrical areas.

DETAILED DESCRIPTION OF THE INVENTION

[0027]FIG. 2 shows the module configuration of a matrix-driven typedisplay unit 10. The display unit 10 has the structure that aluminescent layer 16 is sandwiched between two insulating layers 14 and18 on a substrate 12 which is made of glass, ceramic, or the like. Aplurality of data electrodes 20 are arranged in parallel on thesubstrate 12. A plurality of scanning electrodes 22 are arranged inparallel on the insulating layer 18, at right angles to the dataelectrodes 20. When the display unit 10 displays a white window, thescanning electrodes 22 in the window-displaying area can cause voltagedrops with a crosstalk phenomenon as shown in FIG. 1 if the signallevels set as the respective pixel values are applied to the scanningelectrodes as is.

[0028] Then, in the present embodiment, the pixel values, i.e., thesignal levels shall be corrected through signal processing to suppressthe occurrence of crosstalk. While FIG. 2 shows the configuration of thedisplay unit 10 of an organic EL panel, inorganic EL panel, or the likewhich has the luminescent layer 14, the display unit 10 may be formed asa matrix-driven type liquid crystal panel.

[0029]FIG. 3 shows the configuration of a display processor 1 accordingto the embodiment. The display processor 1 comprises an input unit 2, anintegration unit 3, an average obtaining unit 4, a line memory 5, adifference value operation unit 6, a processing unit 7, and the displayunit 10. The display unit 10 is provided with a display panel and adriving circuit for matrix driving.

[0030] The input unit 2 initially accepts an image signal and suppliesit to the line memory 5. The line memory 5 stores the image signal for asingle line of the display unit 10, i.e., the pixel values of a linefulof pixels. The integration unit 3 integrates the lineful of pixel valuesstored in the line memory 5. In this example, the integration unit 3integrates the pixel values simultaneously with the input of the imagesignal to the line memory 5. Nevertheless, the pixel values may beintegrated at any timing, such as when they are output from the linememory 5. When a lineful of image signal is input to the line memory 5,the integration unit 3 transmits the integrated value of the lineful ofpixel values to the average obtaining unit 4. The average obtaining unit4 divides the integrated value of the pixel values by the number ofpixels, thereby calculating and obtaining the average of the pixelvalues on that line. Incidentally, in such cases that the image signalis read from its source with previously-calculated averages, the averageobtaining unit 4 may accept those averages. In the case of FIG. 1, theaverage pixel value on the line A-A′ is expressed as(0.3×r+0.7×(q−p))/r. The average pixel value on the line B-B′ is 0.3.

[0031] The difference value operation unit 6 receives the average pixelvalue for a single line from the average obtaining unit 4. Thedifference value operation unit 6 calculates pixel difference valuesbetween this average pixel value and the pixel values of the targetpixels to be corrected, i.e., the signal levels output from the linememory 5. The target pixels to be corrected may be all the lineful ofpixels. The pixel difference values calculated are sent to theprocessing unit 7.

[0032]FIG. 4 shows the configuration of the processing unit 7. Theprocessing unit 7 has a difference value obtaining unit 31, a correctionlevel determination unit 32, a variation obtaining unit 33, a gaindetermination unit 34, and a correction unit 35. The difference valueobtaining unit 31 obtains pixel difference values from the differencevalue operation unit 6, and transmits the same to the correction leveldetermination unit 32. Based on the pixel difference values, thecorrection level determination unit 32 determines the correction levelof the pixel values to be corrected. The correction level is a factor tobe added/subtracted to/from the original pixel values by the correctionunit 35.

[0033]FIG. 5 shows an example of a correction level controlcharacteristic. The abscissa represents the pixel difference value, andthe ordinate the correction level. According to this correction levelcontrol characteristic, a correction level can be set uniquely for eachpixel difference value. The inventor has confirmed that the greater apixel difference value, i.e., the difference between the average pixelvalue and a target pixel value to be corrected is, the greater thebrightness variation occurring from the crosstalk phenomenon is. Basedon the finding, the inventor has contrived the correction level controlcharacteristic that increases the correction level with an increase inthe absolute value of the pixel difference value. While the correctionlevel control characteristic shown in FIG. 5 is asymmetrical about theorigin point, it may be symmetrical and is preferably set according tosuch factors as the structure of the display unit 10. Returning to FIG.4, the correction level determination unit 32 determines the correctionlevel of the target pixel values by using this correction level controlcharacteristic. The correction unit 35 adds/subtracts the determinedcorrection level to/from the target pixel values to correct the targetpixel values. The pixel values corrected are sent to the driving circuitof the display unit 10, and processed as the signals for thecorresponding pixels.

[0034]FIG. 6 shows an image to appear on the display unit 10 andexamples of the corrected pixel values, or signal levels, on thehorizontal lines. On the line A-A′, a correction level of α isdetermined from the pixel difference values. In the range from pixel 1to pixel (p−1) and in the range from pixel q to pixel r, the signallevels can be set at (0.3+a) to suppress the occurrence of crosstalk. Inthis example, no correction is made to the signal levels in the rangefrom pixel p to pixel (q−1). The correction processing may thus beapplied to only the areas that are greatly affected by voltage drops. Inanother example, the correction processing may be applied to even therange from pixel p to pixel (q−1). On the line B-B′, all the pixelvalues are the average value of 0.3, with pixel difference values of 0.No correction processing is thus applied to the original pixel values.

[0035]FIG. 7 shows an example of a correction gain controlcharacteristic for adjusting the correction level. The abscissarepresents a variation in pixel value near a target pixel to becorrected. The ordinate represents the correction gain. In the presentembodiment, the correction gain and the determined correction level aremultiplied and used as the factor for adjusting the amount of correctionof target pixels. According to this correction gain controlcharacteristic, a correction gain can be set uniquely for each variationin the pixel value near a target pixel to be corrected. Incidentally,the correction gain control characteristic is preferably set accordingto such factors as the configuration of the display unit 10.

[0036] Crosstalk tends to occur when generally uniform images aredisplayed on the display unit 10, and less likely when minute patternsare displayed. In view of this, variations in the pixel values ofadjacent pixels of a target pixel to be corrected, lying on the sameline, are determined to evaluate crosstalk-based brightness variations.The correction level determined by the correction level determinationunit 32 is then adjusted.

[0037]FIG. 8 is a diagram for explaining an example of the method forcalculating variations. The variation obtaining unit 33 receives alineful of pixel values from the line memory 5, and determinesvariations. Initially, three adjacent pixels of a target pixel to becorrected, lying on the same horizontal line, are assumed in eitherdirection. The numbers of pixels are not limited to three, but arepreferably set symmetrically wherever possible. As shown in the diagram,the pixels shall have pixel values of (P−3), (P−2), (P−1), P0, P1, P2,and P3, staring from the left.

[0038] The variation obtaining unit 33 determines differences betweenthe pixel values of adjoining pixels out of the assumed pixels, anddetermines the absolute values thereof. In this case, the variationobtaining unit 33 calculates |(P−3)−(P−2)|, |(P−2)−(P−1)|, |(P−1)−P0)|,|P1−P0|, |P2−P1|, and |P3−P2| as pixel difference absolute valuesbetween the adjoining pixels. Then, the variation obtaining unit 33determines an integrated value thereof as a variation. In the case ofuniform display containing fewer brightness variations as a whole, pixeldifference values between adjoining pixels become smaller. Then, theintegrated value of the absolute values thereof, or variation, alsobecomes smaller. Consequently, when variations are small, the displaycan be evaluated as being uniform, which means that the display tends tocause crosstalk. By contrast, when the integrated values of the pixeldifference absolute values are great, the display can be evaluated asincluding minute patterns or the like. This means that the display isless likely to cause crosstalk.

[0039] As described above, the variation obtaining unit 33 obtains theintegrated value of the pixel difference absolute values between theadjoining pixels near a target pixel to be corrected as the variation.Then, the gain determination unit 34 can determine the correction gainbased on the correction gain control characteristic shown in FIG. 7.This correction gain control characteristic is such that the correctiongain decreases with an increasing variation and increases with adecreasing variation. As mentioned previously, the reason for this isthat great variations arise when crosstalk is less likely to occur, andthe amount of correction of the pixel values thus need not be high. Whenvariations are small, on the other hand, the amount of correction of thepixel values must be high since the display tends to cause crosstalk.Consequently, when variations are great, the gain determination unit 34determines a correction gain which decreases the amount of correction ofthe target pixel values. When variations are small, the gaindetermination unit 34 determines a correction gain which increases theamount of correction. The correction unit 35 multiplies the correctionlevel by the correction gain, and corrects the target pixel values byadding/subtracting the multiplied value to/from the target pixel values.

[0040] In the example described above, the pixel difference absolutevalues between pixels are integrated at the time of obtainingvariations. Nevertheless, in preparation for the case where pixel valuesvary sharply, variations may be obtained effectively by using athreshold. Referring to the example of display in FIG. 1, the pixelvalues at the edges on the line A-A′, such as at pixels p and q, varysharply from those of the adjoining pixels. On this account, if pixels pand q themselves or adjacent pixels are to be corrected, the pixeldifference absolute values between adjoining pixels increasesignificantly at the edges. When the integrated values thereof areregarded as variations, the great differences in pixel value at theedges can thus result in the evaluation that the display is high inpixel value variation even if the display is uniform except at theedges. Then, the variation obtaining unit 33 shall compare pixeldifference absolute values with a predetermined threshold, and if thethreshold is exceeded, determine the integrated value of the pixeldifference absolute values by integrating the threshold instead of thepixel difference absolute values. As a result, excessively-large pixeldifference absolute values can be replaced with a predetermined valuewhen edges arise at some points, i.e., when the pixel values varysharply. This enhances the reliability of the variations which areobtained for the sake of grasping the display characteristic.

[0041] In another example, variations can be obtained by using only theresults of comparison between the calculated pixel difference absolutevalues and a threshold. In this case, the pixel difference absolutevalues and the threshold are compared, and the number of pixeldifference absolute values that exceed the threshold is counted. Thiscan absorb the impact of sharp changes in pixel value upon the variationcalculation, making it possible to obtain variations with higherreliability.

[0042]FIG. 9(a) shows an example of display on the display unit 10 andthe input signal levels when uneven crosstalk occurs. This phenomenonresults from pixel-by-pixel differences in voltage drop due to the factthat the display unit 10 varies in resistance from one pixel position toanother. This FIG. 9(a) shows how the level of brightness variationchanges depending on the pixel positions of the display unit 10 on theline A-A′. In such a case, the gain determination unit 34 determines thecorrection gain in accordance with pixel positions on the display unit10.

[0043] For example, the gain determination unit 34 may determine thecorrection gain based on the distance from an end of the line. If thepower is supplied from line ends, the voltage drop increases inward. Itis thus preferable that the gain determination unit 34 determine thecorrection gain taking account of those variations in voltage drop.

[0044]FIG. 9(b) shows the signal level which corrects the target pixelvalues in accordance with the positions of the target pixels to becorrected on the display unit 10. On the line A-A′, thecrosstalk-occurring areas are given position-based amounts ofcorrection. More specifically, in the range from pixel 1 to pixel (p−1)and in the range from pixel q to pixel r, the amounts of correction havegradients. This makes it possible to suppress crosstalk-based brightnessvariations depending on pixel positions, thereby achieving preferablescreen display.

[0045]FIG. 10(a) shows an example of display on the display unit 10 andthe input signal levels when crosstalk occurs at the boundaries betweencrosstalk-occurring areas and crosstalk-free areas. In this example, ablack window is displayed. The occurrence of crosstalk on horizontallines also causes crosstalk in the vertical directions. Morespecifically, in this phenomenon, horizontal-line crosstalk occurs onthe line A-A′, and vertical crosstalk also occurs at the two boundariesdesignated by the lines C-C′.

[0046]FIG. 10(b) shows the signal levels for suppressing the crosstalkat the boundaries to correct the target pixel values. Initially, theboundaries are detected by utilizing the average pixel values ofhorizontal lines. The average pixel value of the line A-A′ is expressedas 0.7×(p+r−q)/r. The average pixel value of the line B-B′ is 0.7. Aswith the line A-A′, the average pixel values of the lines C-C′ at theboundaries are also expressed as 0.7×(p+r−q)/r. Incidentally, theintegrated values of the pixel values on the horizontal lines may beused instead of the average pixel values.

[0047] Returning to FIGS. 3 and 4, the average obtaining unit 4 obtainsthe average pixel values of a plurality of horizontal lines, andsupplies the same to the difference value operation unit 6. Thedifference value operation unit 6 determines differences between theaverage pixel values of lines adjoining vertically, thereby calculatingline difference values. The difference value obtaining unit 31 of theprocessing unit 7 receives the line difference values calculated.

[0048] In the example of display shown in FIG. 10(a), the horizontallines in the crosstalk-occurring area and in the crosstalk-free areashave the same respective average pixel values. Thus, the line differencevalues calculated within these areas are zero. Meanwhile, the boundariesbetween the occurring area and the free areas, i.e., the horizontallines C-C′ have a line difference value which is given by0.7−(0.7×(p+r−q)/r)=0.7×(q−p)/r. If the line difference values exceed apredetermined threshold, the difference value obtaining unit 31determines that the lines are boundaries.

[0049]FIG. 11 shows another example of the correction gain controlcharacteristic for adjusting the correction level. The abscissarepresents the line difference value, and the ordinate the correctiongain. In the present embodiment, the correction gain and the determinedcorrection level are multiplied and used as the factor for adjusting theamount of correction of target pixels. According to this correction gaincontrol characteristic, a correction gain can be set uniquely for eachline difference value. Take, for example, the case where the line A-A′has a correction level of α as described so far. If the correction gainof the lines C-C′ is set to G by using the correction gain controlcharacteristic shown in FIG. 11, the pixel values on the lines C-C′ arecorrected to (0.7−α×G). Crosstalk occurring in the directions orthogonalto the lines increases brightness variations depending on the linedifference values. Thus, the correction gain control characteristic isset so as to increase the correction gain with an increasing linedifference value, and decrease the correction gain with a decreasingline difference value.

[0050] Consequently, on the lines C-C′ of FIG. 10(b), the signal levelsare set to (0.7−α×G). Since the target pixel values are correctedaccording to the line difference values between the horizontal lines, itbecomes possible to suppress the crosstalk that occurs in the verticaldirections.

[0051]FIG. 12(a) shows an example of display where crosstalk occursbetween symmetrical areas on the display unit 10. The display unit 10 issometimes split into a plurality of areas for driving, by such a methodas vertical split driving. Given this case, i.e., when the display unit10 is vertically split for driving, the supply of power in one of theareas can affect the brightness of the pixels at symmetrical positionsin the other area because of symmetrical driving. As shown in FIG.12(a), crosstalk can thus occur on a line C-C′ which lies in theposition symmetrical to the line A-A′.

[0052]FIG. 12(b) shows the signal levels for suppressing the crosstalkat the symmetrical position, thereby correcting the target pixel values.In this case, for example, the line A-A′ and the line C-C′ may beconsidered as a single horizontal line and corrected by the methoddescribed above. Even if the line A-A′ includes a window area, pixelvalues can be corrected accordingly as described previously. It istherefore possible to suppress the crosstalk which has occurred on theline C-C′ in the position symmetrical to the line A-A′, therebypromising preferable image quality.

[0053] Up to this point, the present invention has been described inconjunction with the embodiment. This embodiment is given solely by wayof illustration. It will be understood by those skilled in the art thatvarious modifications may be made to combinations of the foregoingcomponents and processes, and all such modifications are also intendedto fall within the scope of the present invention. While the embodimenthas chiefly dealt with the case of displaying a white window, the pixelvalues can be corrected similarly even in displaying a black window.Moreover, in the embodiment, the pixel values are averaged for eachsingle line. This is not restrictive, however. A target pixel value maybe corrected by using an average of pixel values in a predetermined areaon the line.

What is claimed is:
 1. A display processor comprising: a first obtainingunit which obtains an average pixel value, or an average of pixel valuesin a predetermined area on a line; an operation unit which calculates apixel difference value, or a difference between the average pixel valueand a pixel value of a target pixel to be corrected; a processing unitwhich corrects the target pixel value, or the pixel value of the targetpixel, according to the pixel difference value; and a display unit whichdisplays the pixel value corrected.
 2. The display processor accordingto claim 1, wherein the processing unit comprises: a second obtainingunit which obtains a variation in pixel value near the target pixel; anda correction unit which corrects the target pixel value according to thevariation.
 3. The display processor according to claim 2, wherein theprocessing unit decreases the amount of correction of the target pixelvalue with an increasing variation, and increases the amount ofcorrection of the target pixel value with a decreasing variation.
 4. Thedisplay processor according to claim 2, wherein the second obtainingunit obtains the variation based on adjoining-pixel difference absolutevalues, or absolute values of differences between the pixel values ofpixels adjoining within a certain area near the target pixel.
 5. Thedisplay processor according to claim 3, wherein the second obtainingunit obtains the variation based on adjoining-pixel difference absolutevalues, or absolute values of differences between the pixel values ofpixels adjoining within a certain area near the target pixel.
 6. Thedisplay processor according to claim 4, wherein the second obtainingunit obtains the variation based on an integrated value of theadjoining-pixel difference absolute values.
 7. The display processoraccording to claim 5, wherein the second obtaining unit obtains thevariation based on an integrated value of the adjoining-pixel differenceabsolute values.
 8. The display processor according to claim 4, whereinif an adjoining-pixel difference absolute value exceeds a threshold, thesecond obtaining unit determines an integrated value by subjecting thethreshold to the integration instead of the adjoining-pixel differenceabsolute value.
 9. The display processor according to claim 5, whereinif an adjoining-pixel difference absolute value exceeds a threshold, thesecond obtaining unit determines an integrated value by subjecting thethreshold to the integration instead of the adjoining-pixel differenceabsolute value.
 10. The display processor according to claim 2, whereinthe second obtaining unit compares each of the adjoining-pixeldifference absolute values between adjoining pixels within a certainarea near the target pixel with a threshold, and obtains the variationbased on the counted number of adjoining-pixel difference absolutevalues exceeding the threshold.
 11. The display processor according toclaim 3, wherein the second obtaining unit compares each of theadjoining-pixel difference absolute values between adjoining pixelswithin a certain area near the target pixel with a threshold, andobtains the variation based on the counted number of adjoining-pixeldifference absolute values exceeding the threshold.
 12. The displayprocessor according to claim 4, wherein the second obtaining unitcompares each of the adjoining-pixel difference absolute values betweenadjoining pixels within a certain area near the target pixel with athreshold, and obtains the variation based on the counted number ofadjoining-pixel difference absolute values exceeding the threshold. 13.The display processor according to claim 5, wherein the second obtainingunit compares each of the adjoining-pixel difference absolute valuesbetween adjoining pixels within a certain area near the target pixelwith a threshold, and obtains the variation based on the counted numberof adjoining-pixel difference absolute values exceeding the threshold.14. The display processor according to claim 1, wherein the processingunit corrects the target pixel value according to the position of thetarget pixel on the display unit.
 15. The display processor according toclaim 1, wherein the first obtaining unit obtains the averages orintegrated values of the pixel values in predetermined areas on aplurality of lines including the predetermined area on the line, theoperation unit calculates a line difference value, or a differencebetween the average pixel values or integrated values of the lines, andthe processing unit corrects the target pixel value according to theline difference value.
 16. The display processor according to claim 1,wherein when the display unit is split into a plurality of areas fordriving, the processing unit corrects the pixel value of a pixel at aposition symmetrical to the target pixel in the split area.
 17. Aninorganic EL display processor comprising: a first obtaining unit whichobtains an average pixel value, or an average of pixel values in apredetermined area on a line; an operation unit which calculates a pixeldifference value, or a difference between the average pixel value and apixel value of a target pixel to be corrected; a processing unit whichcorrects the target pixel value, or the pixel value of the target pixel,according to the pixel difference value; and a display unit whichdisplays the pixel value corrected.
 18. The inorganic EL displayprocessor according to claim 17, wherein the processing unit comprises:a second obtaining unit which obtains a variation in pixel value nearthe target pixel; and a correction unit which corrects the target pixelvalue according to the variation.
 19. An organic EL A display processorcomprising: a first obtaining unit which obtains an average pixel value,or an average of pixel values in a predetermined area on a line; anoperation unit which calculates a pixel difference value, or adifference between the average pixel value and a pixel value of a targetpixel to be corrected; a processing unit which corrects the target pixelvalue, or the pixel value of the target pixel, according to the pixeldifference value; and a display unit which displays the pixel valuecorrected.
 20. The organic EL display processor according to claim 19,wherein the processing unit comprises: a second obtaining unit whichobtains a variation in pixel value near the target pixel; and acorrection unit which corrects the target pixel value according to thevariation.